It wasn't immediately clear to what Trump was referring, but last week host Mika Brzezinski railed against Trump for calling Democratic presidential nominee Hillary Clinton a "bigot."

"We were just talking off-set, and I have to say it," Brzezinski said. "Donald Trump, you have no idea what your words mean. You have no idea. You have no idea what your words mean."

She continued: "I can't pretend and sort of try and cover this fairly and put it in the veil of objectivity. This is wrong. You have no idea what your words mean and what you're doing to this country."

"Morning Joe" has been increasingly critical in its coverage of Trump. Earlier this week, host Joe Scarborough started calling Trump "Amnesty Don," using Trump's tendency to come up with nicknames for his opponents to mock the candidate's softening on immigration, his signature issue.

Scarborough followed the new nickname with a music video that chided everything from Trump's appearance to his proposed immigration policies.

Republican presidential nominee Donald Trump walks with Mexico President Enrique Pena Nieto at the end of their joint statement at Los Pinos, the presidential official residence, in Mexico City, Wednesday, Aug. 31, 2016. Trump is calling his surprise visit to Mexico City Wednesday a 'great honor.' The Republican presidential nominee said after meeting with PeÃ±a Nieto that the pair had a substantive, direct and constructive exchange of ideas.(AP Photo/Dario Lopez-Mills)

Mexico's President Enrique Pena Nieto speaks during a a joint statement with Republican presidential nominee Donald Trump in Mexico City, Wednesday, Aug. 31, 2016. Trump is calling his surprise visit to Mexico City Wednesday a 'great honor.' The Republican presidential nominee said after meeting with PeÃ±a Nieto that the pair had a substantive, direct and constructive exchange of ideas.(AP Photo/Dario Lopez-Mills)

Republican presidential nominee Donald Trump speaks during a joint statement with Mexico's President Enrique Pena Nieto in Mexico City, Wednesday, Aug. 31, 2016. Trump is calling his surprise visit to Mexico City a 'great honor.' The Republican presidential nominee said after meeting with PeÃ±a Nieto that the pair had a substantive, direct and constructive exchange of ideas. (AP Photo/Dario Lopez-Mills)